Unfortunately I'm not currently in a position where I can offer my sail repair services. The best bet for a decent repair would be HD sails (Jim Hunt and Andy Davies)
www.hdsails.com They are based somewhere around the birmingham area.
Another option would be
www.peakdinghy.co.uk They are based in Chesterfield and offer repairs but do not have experience in sail making so not a great option if your after any modifications or anything other than small patches.
As a final resort there is always P+B
www.pinbax.com but they're generally expensive and no better for repairs than anyone else.
There are actually a couple of others in the midlands that I would recommend avoiding but i'll not name and shame.
Hope that helps